Cloud computing is becoming popular as people have multiple network devices such as a mobile phone besides their Mac/PC. Cloud computing is inevitable when a person wants to keep his personal data such as Mail, Contacts, Calendar and other data in synchronization among the devices. There are already some cloud services running on the Internet. But cloud computing does not lend itself well to content that a person purchases on online stores. The person might be able to “share” the content among his devices if Digital Rights Management (DRM) allows, but this is not always the case. The content tends to be bound to a device to prevent a copy-back attack or for security/business reasons. This makes it difficult to manage the content on a server and utilize the content on a cloud computing type of service. Even if DRM allows sharing content, copying or streaming the content locally between devices is not sufficient when the person is no longer able to rely on a PC or local server. Even if a device is able to decrypt the content, this does not necessarily mean the content is able to be played back/viewed on that device because of differences of the video profiles or a necessity of metadata, for example. In addition, local sharing is not related to global “sync.” For example, a person is not able to purchase content on a home computer and then use the content in a tent (e.g. on a mobile device). On the other hand, it appears easy to share protected content among the devices using a centric server if the content is not bound to a device, as long as the provider disclaims control of the content, for example, a case where the provider sells the content, and a user is able to copy it freely among registered devices. But if the provider wishes to keep the control of the content (e.g. a case of rental content), this model obviously does not work.